linux-kernel - [PATCH 09/10] NOMMU: Teach kobjsize() about VMA regions. [ver #3]

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Message-ID: <20090108125432.28454.98069.stgit@warthog.procyon.org.uk>
Date:	Thu, 08 Jan 2009 12:54:32 +0000
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	bernds_cb1@...nline.de, dhowells@...hat.com,
	rgetz@...ckfin.uclinux.org, vapier.adi@...il.com,
	lethal@...ux-sh.org, linux-kernel@...r.kernel.org
Subject: [PATCH 09/10] NOMMU: Teach kobjsize() about VMA regions. [ver #3]

From: Paul Mundt <lethal@...ux-sh.org>

Now that we no longer use compound pages for all large allocations,
kobjsize() actively breaks things like binfmt_flat by always handing
back PAGE_SIZE for mmap'ed regions. Fix this up by looking up the
VMA region for non-compounds.

Ideally binfmt_flat wants to get rid of kobjsize() completely, but
this is an incremental step.

Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
Signed-off-by: David Howells <dhowells@...hat.com>
Tested-by: Mike Frysinger <vapier.adi@...il.com>
---

 mm/nommu.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)


diff --git a/mm/nommu.c b/mm/nommu.c
index a6e8ccf..60ed837 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -149,6 +149,20 @@ unsigned int kobjsize(const void *objp)
 		return ksize(objp);
 
 	/*
+	 * If it's not a compound page, see if we have a matching VMA
+	 * region. This test is intentionally done in reverse order,
+	 * so if there's no VMA, we still fall through and hand back
+	 * PAGE_SIZE for 0-order pages.
+	 */
+	if (!PageCompound(page)) {
+		struct vm_area_struct *vma;
+
+		vma = find_vma(current->mm, (unsigned long)objp);
+		if (vma)
+			return vma->vm_end - vma->vm_start;
+	}
+
+	/*
 	 * The ksize() function is only guaranteed to work for pointers
 	 * returned by kmalloc(). So handle arbitrary pointers here.
 	 */

--
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